Frequency response

About: Frequency response is a research topic. Over the lifetime, 25705 publications have been published within this topic receiving 332249 citations.

On Frequency Response Curves in Rooms. Comparison of Experimental, Theoretical, and Monte Carlo Results for the Average Frequency Spacing between Maxima

Abstract: The average frequency spacing 〈Δfmax〉 between adjacent maxima of the frequency response curve between two points in a room is determined by experiment, theory, and Monte Carlo computation. In earlier papers it had been shown that, above a certain critical frequency, 〈Δfmax〉 is reciprocally related to reverberation time and not dependent on other room characteristics—disproving a belief that 〈Δfmax〉 is a useful measure of the acoustical quality of rooms. Theory predicts 〈Δfmax〉 = 3.91/T60, where T60 is the reverberation time. Monte Carlo computation gives 3.90/T60. Measurements in two very different rooms using a vacuum tube voltmeter for reading the sound pressure are in good agreement with these predictions. Measurements with a logarithmic level recorder give, as in earlier investigations, much larger values. The discrepancy cannot be explained by the level recorder's 0.5‐db quantization. This paper shows that: (1) The Monte Carlo method is a useful tool for solving complex problems in room acoustics. (2...

A New Approach to Modeling Multiport Systems From Frequency-Domain Data

Abstract: This paper addresses the problem of modeling systems from measurements of their frequency response. For multiport devices, currently available techniques are expensive. We propose a new approach which is based on a system-theoretic tool, the Loewner matrix pencil constructed in the context of tangential interpolation. Several implementations are presented. They are fast, accurate, they build low order models and are especially designed for a large number of terminals. Moreover, they identify the underlying system, rather than merely fitting the measurements. The numerical results show that our algorithms yield smaller models in less time, when compared to vector fitting.

Variable Frequency Controller for Inductive Power Transfer in Dynamic Conditions

Abstract: Inductive power transfer is a highly attractive option for powering unmanned aerial or underwater vehicles, in harsh environments and while in continuous motion. This study presents a variable frequency controller for series–series compensated contactless chargers operating in dynamic conditions. The controller tracks, in real time, the frequency for which the output voltage is load independent. The criterion for that is the zeroing of the phase difference between the secondary current and the primary-side inverter output voltage. Control is performed by a phase-locked loop with optical communication between the two sides. Experimental results on a 1-kW prototype, for power transfer while in motion, show fast frequency response, along with steady output voltage, despite load variations. Comparison is performed with two other fixed frequencies of operation; the natural frequency of the primary resonant circuit and the maximum output power frequency at nominal gap. The proposed control is proven superior in terms of output power level and stability, as well as safety to highly misaligned conditions.

A Narrow-Passband and Frequency-Tunable Microwave Photonic Filter Based on Phase-Modulation to Intensity-Modulation Conversion Using a Phase-Shifted Fiber Bragg Grating

Abstract: A novel approach to implementing a narrow-passband and frequency-tunable microwave photonic filter (MPF) based on phase-modulation to intensity-modulation conversion in a phase-shifted fiber Bragg grating (PS-FBG) is proposed and experimentally demonstrated. In the proposed MPF, a phase-modulated signal is sent to a PS-FBG. If one of the sidebands falls in the notch of the PS-FBG, the phase-modulated signal is converted to an intensity-modulated signal. Due to the ultra-narrow notch of the PS-FBG, a microwave filter with an ultra-narrow passband is realized. The tunability of the microwave filter is achieved by tuning the wavelength of the optical carrier. A theoretical analysis is performed in which the value of the phase shift and the location of the phase shift in the PS-FBG on the frequency response of the MPF are studied. Two PS-FBGs with different reflection bandwidths and different phase-shift values introduced at the center of the gratings are fabricated and incorporated into the proposed MPF. For the two PS-FBGs, the 3-dB bandwidths are 120 and 60 MHz and the tunable ranges are 5.5 and 15 GHz.